1. Field of the Invention
The present invention relates to an interface circuit for performing communication with an upstream device and with a system controller, a disc controller including such an interface circuit, a disc drive apparatus including such an interface circuit, and an interface control method. The system controller is provided for controlling the disc drive apparatus.
2. Description of the Related Art
Recently, optical disc drive apparatuses (for example, DVD-RAM drives) are used as memory devices mounted on personal computer systems, DVD recorder systems and the like.
As a host interface for connecting an optical disc drive apparatus and a host device, an IDE interface is well known. Especially today, an ATA/ATAPI interface (hereinafter, referred to also as the “ATAPI interface”) is well known, which has been standardized by the American National Standards Institute (ANSI) and is being standardized by the Technical Committee TB13. The ATA (AT attachment) is a standard for connection of a hard disc, and ATAPI (ATA Packet Interface) is a standard for connection of an assisting memory device other than the hard disc, such as a DVD-RAM drive or the like.
The ATAPI interface includes a register, from which data can be read and to which data can be written by, for example, (i) an optical disc controlling microcomputer (hereinafter, referred to as the “optical disc controller” or “ODC”) included in a drive apparatus or the like, or a system controlling microcomputer (hereinafter, referred to as the “system controller”) for controlling the entirety of elements included in an optical disc drive apparatus, and (ii) also by a host device. This register is referred to as a task file register (or an ATA register).
Today, new products used for optical disc drive apparatuses (for example, DVD-RAM drives) are marketed substantially every year. Corporations and engineers who develop optical disc drive apparatuses wish to accelerate the speed of development of the optical disc drive apparatuses and produce and market new products of optical disc drive apparatuses as rapidly as possible. They especially wish to increase the speed of development of system controllers for the purpose of increasing the speed of development of the optical disc drive apparatuses. Engineers involved in developing system controllers wish to reduce the load of development of system controllers, which requires each element of LSI hardware (for example, optical disc controllers) controlled by the system controllers to have more diverse functions.
One means for increasing the, speed of development of system controllers is to have LSI hardware (e.g., optical disc controllers) perform control processing, which is conventionally performed by system controllers. In this way, the number of steps for developing the system controllers is reduced.
Such processing, which is conventionally performed by the system controllers and is to be performed by the LSI hardware, is desired to be common between corporations (for example, to be made uniform by a standard) in consideration of sales of LSI.
One example of processing made uniform by a standard is made uniform by “Information Technology AT Attachment with Packet Interface-6 (ATA/ATAPI-6)”, which is a standard of the ATA/ATAPI interface. Hereinafter, ATA/ATAPI-6 will be referred to as the “ATAPI Standard”. The ATAPI Standard defines various types of processing as protocols.
The ATAPI Standard protocol processing is conventionally performed by system controllers despite being made uniform by the Standard.
Under the circumstances, a method for performing the conventional ATAPI Standard protocol processing using LSI hardware such as optical disc controllers instead of system controllers is proposed (see, for example, Japanese Laid-Open Publication No. 2001-325204).
According to the method for performing the conventional ATAPI Standard protocol processing described in Japanese Laid-Open Publication No. 2001-325204, control processing, which is conventionally performed by a system controller (for example, processing for setting registers for a host interface including a task file register or the like), is executed by an optical disc controller acting as LSI hardware.
The processing for setting registers is, more specifically, for example, processing for setting a task file register, such as an error register or a status register. Such processing is performed in order to notify the host device of a command execution result. Such processing, which is conventionally performed by a system controller as processing as a command issued by the host device, is executed by an optical disc controller acting as LSI hardware.
This releases the engineers involved in developing system controllers from the work of development regarding the ATAPI Standard protocol processing, which is conventionally executed by the system controllers, and alleviates the load on system controller development.
However, the method described in Japanese Laid-Open Publication No. 2001-325204 has the following problem. Since the ATAPI Standard protocol processing is executed via the LSI hardware, the system controller cannot directly access the ATAPI interface. Thus, for example, the customization of the interface circuit, which is conventionally performed using the system controller, for controlling LSI hardware as an operation inherent in the drive, by directly setting the registers in the ATAPI interface, becomes very difficult. Although the load of development of system controllers is reduced, the efficiency of development of system controllers is deteriorated.
The optical disc controller described in Japanese Laid-Open Publication No. 2001-325204 can automatically execute the ATAPI Standard protocol processing, but it is very difficult for such an optical disc controller to execute customization using the system controllers.